<!DOCTYPE html>

<html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>链接外部样式</title>

        <!-- 通过 link 链接外部样式文件 -->
        <link rel="stylesheet" href="external.css" >

    </head>
    <body>

        <div class="wrapper">
            <div class="left"></div>
            <div class="center"></div>
            <div class="right"></div>
        </div>

    </body>
</html>